# user-space tools which handle kernel control groups mechanism. We want to improve them where necessary and feasible and/or to create new ones e.g. to create or modify cgroups configuration or display control groups data (using [http://libcg.sourceforge.net/ libcgroups] package).

# user-space tools which handle kernel control groups mechanism. We want to improve them where necessary and feasible and/or to create new ones e.g. to create or modify cgroups configuration or display control groups data (using [http://libcg.sourceforge.net/ libcgroups] package).

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== Owner ==

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== Owners ==

* Linda Wang

* Linda Wang

** email: lwang@redhat.com

** email: lwang@redhat.com

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== Current status ==

== Current status ==

* Targeted release:[[Releases/11 | Fedora 11 ]]

* Targeted release:[[Releases/11 | Fedora 11 ]]

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** kernel part:

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* Last updated: 2009-04-14

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* Overall CGROUP infrastructure [completed, in Fedora 10]

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* Percentage of completion: 100%

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* Sub-CGROUP features:

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* CPUSET [completed, in Fedora 10]

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* CPUACCT [completed, in Fedora 10]

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* MEMCTL [completed, in Fedora 10]

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* DEVICE [completed, in Fedora 10]

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* NETWORKING [new, targeted for Fedora 11]

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** tools part

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* man-pages

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* code review

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* spec-file cleanup

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* make file cleanup

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* ps option for cgroups

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* new tools

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* Last updated: 2009-02-19

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* Percentage of completion: 65%

== Detailed Description ==

== Detailed Description ==

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== Scope ==

== Scope ==

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== Scope ==

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* Kernel Part:

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===Kernel Part===

There are several sub-features under control group:

There are several sub-features under control group:

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* CGROUPS (grouping infrastructure mechanism)

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* CGROUPS (grouping infrastructure mechanism)

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CGROUPS=y

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* CPUSET (cpuset controller, in F10)

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* CPUACCT (cpu account controller, in F10)

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* CPUSET (cpuset controller, in F10)

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* SCHED (schedule controller, in F10)

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CPUSET=y

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* MEMCTL (memory controller, in F10)

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* DEVICES

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* CPUACCT (cpu account controller, in F10)

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* NETCTL (network controller, new in Rawhide/F11)

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CGROUP_CPUACCT=y

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* SCHED (schedule controller, in F10)

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CGROUP_SCHED=y

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* MEMCTL (memory controller, in F10)

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* tools part:

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RESOURCE_COUNTERS=y

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CGROUP_MEM_CONT=y

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(CGROUP_MEM_RES_CTLR???)

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* DEVICE

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CGROUP_DEVICE=y

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* NETCTL (network controller, New)

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NET_CLS_CGROUP=y

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===tools part===

Required extended testing and fixing of [http://libcg.sourceforge.net/ libcgroups] package and in time when libcgroups will be stable enough try to add start to write another parts - based on existing ones.

Required extended testing and fixing of [http://libcg.sourceforge.net/ libcgroups] package and in time when libcgroups will be stable enough try to add start to write another parts - based on existing ones.

== How To Test ==

== How To Test ==

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For now it is necessary to have a kernel with cgroups support (<code>Documentation/cgroups/cgroups.txt</code>) and the <code>libcgroup</code> package. The user/tester must know, what cgroups are and what they are good for, the best is to read aforementioned kernel doc.

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To help test, and use the control group features in Fedora; there are

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multiple way to test, depends on the feature set that you are interested in.

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From now to other tests it is necessary to have a kernel with cgroups support and the <code>libcgroup</code> package.

Read kernel docs (see below). Each controller should have a documentation there

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====CPUSET====

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* Create a group controlled by cpuset controller, e.g. use following cgconfig.conf:

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<pre>

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mount {

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cpuset = /mnt/cgroup;

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}

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group test {

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perm {

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task {

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uid = root;

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gid = root;

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}

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admin {

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uid = root;

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gid = root;

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}

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}

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# following section is cpuset specific,

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# replace with appropriate content when testing other controllers

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# allow only the first cpu and the first memory region

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cpuset {

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cpuset.cpus = 0;

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cpuset.mems = 0;

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}

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}

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</pre>

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* Start the cgconfig service

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* Execute a task in this group

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<pre>

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$ cgexec -g cpuset:test /bin/bash

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</pre>

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* Check the started bash (and all its children) are in the right group

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<pre>

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$ cat /proc/self/cgroup

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12:cpuset:/test

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$ ps -o cgroup

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...

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</pre>

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* Check, that all children of the bash can use only first cpu (e.g. compile kernel with -j3 or so).

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====CPUACCT====

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* Same as before, use following cgconfig.conf snippet instead of <code>cpuset { }</code>:

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<pre>

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cpuacct {

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}

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</pre>

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* Start a process in the group as before, check, that /mnt/cgroup/test/cpuacct.usage counts CPU cycles of the process and all its future children

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====Memory Controller====

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* Use following cgconfig.conf snippet:

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<pre>

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memory {

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memory.limit_in_bytes = 40M;

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}

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</pre>

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* Again, start something in the group. The process there can use 40 megabytes of memory.

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* Look at /mnt/cgroup/tests/usage_in_bytes,there should be current memory usage of all processes in the group.

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Test other controllers, as described in kernel documentation.

== User Experience ==

== User Experience ==

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Currently, the <code>libcgroups</code> package has several bugs, these will have to be fixed at first. When that is out of the way, configuration (or even monitoring) tools would reduce the barrier of entry to using control groups on Linux significantly.

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End-user who will use this feature will hopefully find it useful to help partition their server/machine resources into different functional units that they can dedicate these resources to.

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The control group user interfaces are very straight forward, and are a set of common easy to use command-line operations. The concept of allocating different system resources such as number of CPUs, amount of memories, and network bandwidth should be easy.

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<code>libcgroups</code> package should help the user to create persistent configuration and would help to reduce the barrier of entry to using control groups on Linux significantly.

== Dependencies ==

== Dependencies ==

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* Depends on kernel > 2.6.24 and <code>libcgroups</code> (current version is 0.32.2) which both are in Fedora since F-9.

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Majority of the implementation is done inside of the kernel.

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Tools part is implemented in package <code>libcgroups</code>

== Contingency Plan ==

== Contingency Plan ==

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The contingency plan for under develop sub-feature is to simply not enable the kernel option during development freeze. Hence it will not expose the incomplete sub-feature to the fedora community.

Currently, nothing depends on <code>libcgroup</code> or the tools which would use it. If things go really wrong, we can always go back to the last working version of <code>libcgroup</code>.

Currently, nothing depends on <code>libcgroup</code> or the tools which would use it. If things go really wrong, we can always go back to the last working version of <code>libcgroup</code>.

[http://libcg.sourceforge.net/ libcgroups] is a tool which helps to manipulate, control and administrate control groups and the associated controllers. Using this tool it is possible to aggregate/partition set of tasks and their future children into hierarchical groups with specialized access to resources.

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Fedora 11 includes a new feature called `Control Group` where it allows system administrator to partition the system resources into different sub groups, and dedicate these sub groups resources to different applications' need. It can be use to dedicate specific applications such as interactive applications; cpu, memory, or network bandwidth intensive application; or database application to a set of pre-allocated system resources.

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The tool consists of two parts -

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* The first one enables user to create persistent cgroups configuration using a configuration file and a service which creates configured groups on startup.

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* The second part enables user to define to which group belong the given process/given processes. This divison is based on uid or gid of processes. The user can start a service which will put the processes to the right subsystem, or there is a tool to move the process to the right subsystem or to create the process in it.

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There is also [http://libcg.sourceforge.net/ libcgroups] tool which helps to manipulate, control and administrate control groups and the associated controllers. Using this tool it is possible to aggregate/partition set of tasks and their future children into hierarchical groups with specialized access to resources.

== Comments and Discussion ==

== Comments and Discussion ==

* See [[Talk:Features/ControlGroups]]

* See [[Talk:Features/ControlGroups]]

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[[Category:FeaturePageIncomplete]]

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[[Category:FeatureAcceptedF11]]

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ControlGroups

Summary

`Control Groups` consists of two parts:

an upstream kernel feature that allows system resources to be partitioned/divided up amongst different processes, or a group of processes.

user-space tools which handle kernel control groups mechanism. We want to improve them where necessary and feasible and/or to create new ones e.g. to create or modify cgroups configuration or display control groups data (using libcgroups package).

Current status

Detailed Description

Kernel Part

Control Groups provide a mechanism for aggregating/partitioning sets of
tasks, and all their future children, into hierarchical groups with
specialized behaviour.

Definitions:

A *cgroup* associates a set of tasks with a set of parameters for one
or more subsystems.

A *subsystem* is a module that makes use of the task grouping
facilities provided by cgroups to treat groups of tasks in
particular ways. A subsystem is typically a "resource controller" that
schedules a resource or applies per-cgroup limits, but it may be
anything that wants to act on a group of processes, e.g. a
virtualization subsystem.

A *hierarchy* is a set of cgroups arranged in a tree, such that
every task in the system is in exactly one of the cgroups in the
hierarchy, and a set of subsystems; each subsystem has system-specific
state attached to each cgroup in the hierarchy. Each hierarchy has
an instance of the cgroup virtual filesystem associated with it.

At any one time there may be multiple active hierachies of task
cgroups. Each hierarchy is a partition of all tasks in the system.

User level code may create and destroy cgroups by name in an
instance of the cgroup virtual file system, specify and query to
which cgroup a task is assigned, and list the task pids assigned to
a cgroup. Those creations and assignments only affect the hierarchy
associated with that instance of the cgroup file system.

On their own, the only use for cgroups is for simple job
tracking. The intention is that other subsystems hook into the generic
cgroup support to provide new attributes for cgroups, such as
accounting/limiting the resources which processes in a cgroup can
access. For example, cpusets (see Documentation/cpusets.txt) allows
you to associate a set of CPUs and a set of memory nodes with the
tasks in each cgroup.

User space tools

Libcgroups makes that functionality available to programmers and contains two tools, cgexec and cgclassify, to start processes in a control group or move existing processes from one control group to another. In Fedora libcgroups package is already incorporated, but the overall quality is very poor. There is almost no documentation, no man pages, no configuration file samples, there should be done code review and created other necessary tools and improve installations:

The goal for Fedora 11 is to improve this package where necessary, i.e.:

bugfixing

add/fix documentation and man-pages

add examples

fix error handling

rework logging

create displaying tool (to see, in which control group is given process)

prepare a way, how to start a service daemon in given context group

The long term goal is to create new tools to e.g. create or modify persistent cgroups configuration and display control groups data.
At the beginning the focus will be on command line tools, but we'll keep in mind that in the long term we'll likely want to have graphical tools. These would offer similar functionality and we should try to make sure that any non-UI code written is usable from both kinds of frontends.

Benefit to Fedora

The implementation of of "control groups" schema and its improvement should enable users to partitioned/divided resources up amongst different processes, or a group of processes.
Libcgroups should helps them to create persistent configuration of partitioning devices and handle cgroups from user point of view. This project should help the user to make the best of control groups kernel feature.

Check, that all children of the bash can use only first cpu (e.g. compile kernel with -j3 or so).

CPUACCT

Same as before, use following cgconfig.conf snippet instead of cpuset { }:

cpuacct {
}

Start a process in the group as before, check, that /mnt/cgroup/test/cpuacct.usage counts CPU cycles of the process and all its future children

Memory Controller

Use following cgconfig.conf snippet:

memory {
memory.limit_in_bytes = 40M;
}

Again, start something in the group. The process there can use 40 megabytes of memory.

Look at /mnt/cgroup/tests/usage_in_bytes,there should be current memory usage of all processes in the group.

Test other controllers, as described in kernel documentation.

User Experience

End-user who will use this feature will hopefully find it useful to help partition their server/machine resources into different functional units that they can dedicate these resources to.

The control group user interfaces are very straight forward, and are a set of common easy to use command-line operations. The concept of allocating different system resources such as number of CPUs, amount of memories, and network bandwidth should be easy.

libcgroups package should help the user to create persistent configuration and would help to reduce the barrier of entry to using control groups on Linux significantly.

Dependencies

Majority of the implementation is done inside of the kernel.
Tools part is implemented in package libcgroups

Contingency Plan

The contingency plan for under develop sub-feature is to simply not enable the kernel option during development freeze. Hence it will not expose the incomplete sub-feature to the fedora community.
Currently, nothing depends on libcgroup or the tools which would use it. If things go really wrong, we can always go back to the last working version of libcgroup.

Release Notes

Fedora 11 includes a new feature called `Control Group` where it allows system administrator to partition the system resources into different sub groups, and dedicate these sub groups resources to different applications' need. It can be use to dedicate specific applications such as interactive applications; cpu, memory, or network bandwidth intensive application; or database application to a set of pre-allocated system resources.

There is also libcgroups tool which helps to manipulate, control and administrate control groups and the associated controllers. Using this tool it is possible to aggregate/partition set of tasks and their future children into hierarchical groups with specialized access to resources.